Google has always done a/b tests to see what users like. This is not new.
Based on the TOS, data can cross products. If you have, for example, different home and work persona, segregate them for real. Either use incognito windows/private browsing, or create different accounts for the different public persona you have. I use both depending on what I am trying to do.

I like Google Plus. Some of the smartest people I've ever read are on Google Plus, and the Hangout is amazing. But Google is doing everything it can to force Google Plus on everyone, and it's pissing me off. Yesterday, I tried to like a video on YouTube. I wasn't signed in to my Google Plus acco...